US Department of Defense
Advancing Blast Injury Research to Protect and Heal Those Who Serve

Early Clinical Measures May Predict Mild TBI Long-Term Health Outcomes

Combat-related traumatic brain injury (TBI), particularly resulting from explosive blast, is a significant concern for Service members and medical providers. Blast-induced TBI is involved in long-term physical and neurocognitive consequences, but predicting the severity experienced, and under what circumstances, is incompletely understood. Previous research into this endeavor has focused on blast-related TBI cases severe enough to warrant medical evacuation from the battlefield, but most Service members who experience head injuries are capable of being treated in theater and remain in combat. Dr. Christine Mac Donald and her colleagues at the University of Washington, Seattle, took steps to address this knowledge gap through a longitudinal, prospective study to determine the long-term effects of blast-related mild TBI on non-medically evacuated Service members and identified predictors of future clinical outcomes.1

In 2012, the study enrolled Service members at Kandahar Air Field and Camp Leatherneck in Afghanistan. Blast-related mild TBI participants (N = 45) were diagnosed with TBI by trained clinicians within days of a blast event; control participants (N = 45) were in the same deployed setting but had a negative TBI screen, and no history of blast exposure. All 90 participants were assessed for an array of symptoms including post-concussive, psychological (post-traumatic stress disorder [PTSD], depressive), and cognitive symptoms within a week of enrollment. At a five-year follow-up, participants underwent neurobehavioral, neuropsychological, and psychiatric evaluations.

Compared to non-concussed controls, mild blast TBI participants experienced more severe levels of disability and had a lower quality of life; they also displayed more severe neurobehavioral symptoms, headaches, neurological deficits (such as loss of hearing and smell), and psychiatric symptoms (PTSD, depression, and anxiety). While almost 80 percent of concussed participants pursued mental health services, fewer than 30 percent experienced lasting symptom improvement.

Using statistical modelling of all participants, the investigators explored predictive relationships between early clinical measures - collected within a week of injury - and long-term health outcomes. TBI diagnosis and symptomatology, and acute symptoms of mental health were found to be strong predictors of disability, neurobehavioral impairment, PTSD severity, and cognitive impairment. Of all the assessments given shortly after injury, the Posttraumatic Stress Disorder Checklist, Military Version (PCL-M) was found to be the best predictor of long-term disability, neurobehavioral impairment, and PTSD symptoms.

These findings demonstrate the significant impact TBI has on Service members, even those who are not medically evacuated following injury. The association between early mental health and concussion symptoms, and clinical outcomes five-years later, reflects evolution, rather than resolution, of post-injury symptoms. This work supports the administration of mental health screening procedures in theater, particularly the PCL-M, which takes only two minutes, to identify potential future negative health effects in injured Service members.


1 Mac Donald CL, Barber J, Patterson J, et al. Association Between 5-Year Clinical Outcome in Patients With Nonmedically Evacuated Mild Blast Traumatic Brain Injury and Clinical Measures Collected Within 7 Days Postinjury in Combat. JAMA network open. 2019;2(1): e186676.

Last modified: 11-Mar-2019